Add unit tests for Router configuration and transport layers

- Implemented tests for RouterConfig, RoutingOptions, StaticInstanceConfig, and RouterConfigOptions to ensure default values are set correctly.
- Added tests for RouterConfigProvider to validate configurations and ensure defaults are returned when no file is specified.
- Created tests for ConfigValidationResult to check success and error scenarios.
- Developed tests for ServiceCollectionExtensions to verify service registration for RouterConfig.
- Introduced UdpTransportTests to validate serialization, connection, request-response, and error handling in UDP transport.
- Added scripts for signing authority gaps and hashing DevPortal SDK snippets.

examples/router/src/Examples.Billing.Microservice/Endpoints/UploadAttachmentEndpoint.cs

@@ -0,0 +1,60 @@
+using System.Text.Json;
+using Microsoft.Extensions.Logging;
+using StellaOps.Microservice;
+
+namespace Examples.Billing.Microservice.Endpoints;
+
+/// <summary>
+/// Endpoint for uploading attachments to an invoice.
+/// Demonstrates streaming upload using IRawStellaEndpoint.
+/// </summary>
+[StellaEndpoint("POST", "/invoices/{id}/attachments", SupportsStreaming = true, TimeoutSeconds = 300)]
+public sealed class UploadAttachmentEndpoint : IRawStellaEndpoint
+{
+    private readonly ILogger<UploadAttachmentEndpoint> _logger;
+
+    public UploadAttachmentEndpoint(ILogger<UploadAttachmentEndpoint> logger)
+    {
+        _logger = logger;
+    }
+
+    public async Task<RawResponse> HandleAsync(
+        RawRequestContext context,
+        CancellationToken cancellationToken)
+    {
+        var invoiceId = context.PathParameters.GetValueOrDefault("id") ?? "unknown";
+
+        var contentType = context.Headers["Content-Type"] ?? "application/octet-stream";
+        _logger.LogInformation(
+            "Uploading attachment for invoice {InvoiceId}, Content-Type: {ContentType}",
+            invoiceId,
+            contentType);
+
+        // Read the streamed body
+        long totalBytes = 0;
+        var buffer = new byte[8192];
+        int bytesRead;
+
+        while ((bytesRead = await context.Body.ReadAsync(buffer, cancellationToken)) > 0)
+        {
+            totalBytes += bytesRead;
+            // In a real implementation, you would write to storage here
+        }
+
+        _logger.LogInformation(
+            "Received {TotalBytes} bytes for invoice {InvoiceId}",
+            totalBytes,
+            invoiceId);
+
+        // Return success response
+        var response = new
+        {
+            invoiceId,
+            attachmentId = $"ATT-{Guid.NewGuid():N}"[..16].ToUpperInvariant(),
+            size = totalBytes,
+            uploadedAt = DateTime.UtcNow
+        };
+
+        return RawResponse.Ok(JsonSerializer.Serialize(response));
+    }
+}